Some interesting peculiarities in the high frequency part of the impedance diagram obtained in the case of iron dissolution in dilute H2SO4 solution

Abstract The iron dissolution was investigated by electrode impedance spectroscopy in 5–100 mM deaerated sulphuric acid. It was found that in contrast to higher concentrations, in dilute electrolytes the double layer capacity calculated from the high frequency part of the impedance diagrams is frequency dependent. We evaluated the impedance diagrams and determined the impedance responsible for the frequency dispersion at high frequencies. An empirical expression was found that describes this impedance. We attribute the frequency dependence of the double layer capacity to the presence of the diffuse layer formed in dilute electrolytes.